Error building latest snapshot

[David Jarvie]

I'm getting an error building the latest snapshot on Linux (with cmake 2.4.1). 
Previous snapshots have built successfully. cmake runs without reporting any 
obvious errors on the terminal, but 'make' reports the following errors 
immediately it is run:

CMake Error: Parse error in cache 
file /home/david/src/svn/obj/kdelibs4_snapshot/CMakeCache.txt. Offending 
entry: Error processing project 
file: /home/david/src/svn/obj/kdelibs4_snapshot/CMakeFiles/CMakeTmpQmake/tmp.pro
CMake Error: Parse error in cache 
file /home/david/src/svn/obj/kdelibs4_snapshot/CMakeCache.txt. Offending 
entry: Error processing project 
file: /home/david/src/svn/obj/kdelibs4_snapshot/CMakeFiles/CMakeTmpQmake/tmp.pro
-- Found Qt-Version 4.1.1
-- Building kdelibs...
[snip]

CMakeCache.txt contains the following error messages:

QT_MOC_EXECUTABLE:FILEPATH=QMAKESPEC has not been set, so configuration cannot 
be deduced.
Error processing project 
file: /home/david/src/svn/obj/kdelibs4_snapshot/CMakeFiles/CMakeTmpQmake/tmp.pro

QT_UIC_EXECUTABLE:FILEPATH=QMAKESPEC has not been set, so configuration cannot 
be deduced.
Error processing project 
file: /home/david/src/svn/obj/kdelibs4_snapshot/CMakeFiles/CMakeTmpQmake/tmp.pro

My Qt installation is 4.1.1, built 2 months ago.

Is there some new requirement for building KDE?

-- 
David Jarvie.